1. Field of the Invention
This invention relates to systems utilized on duplicating machines or printing presses for the purpose of effecting and controlling the feed of sheets of paper, envelopes or the like to the printing or duplicating mechanism of the machine or press, and for receiving from the press, such papers or envelopes after completion of the printing, and conveying the printed papers or envelopes in a regular, synchronous and safe fashion to a point spaced from the press where they can be gathered up and packaged or otherwise suitably discharged.
2. Brief Description of the Prior Art
In my copending application Ser. No. 474,975, filed on May 31, 1974, I describe an improved system for sensing and controlling relatively thin sheets of paper fed one-by-one and in sequence from the top of a stack of such materials located on a vertically movable feed table. Such feed tables and systems are, in general, used on presses and duplicating machines. The system disclosed in my copending application improves the reliability of feeding such papers from the top of a stack where the materials fed are a highly compressible stock, such as envelopes and cockle finish onion skin.
In feeding systems of the general type described, a procedure is sometimes followed which is known as "two-up" printing. In this procedure, two side-by-side vertical stacks of relatively narrow stock, such as envelopes, are placed on the feed table and the top items in each of the two stacks are fed simultaneously to the press and are concurrently printed. A problem is encountered in employing this procedure of irregularity or misalignment developing at the tops of the two stacks such that the uppermost sheet or envelope in one stack will be significantly higher than the uppermost sheet or envelope in the other stack. When this occurs, mis-feeding results, some of the product is damaged and in many cases, the press or duplicator must be stopped to clear the machine and realign or level the upper surfaces of the two stacks. Thus, although some increase in production is achieved when a press or duplicator is operated in a two-up fashion, such operations are now conducted in a less than optimum mode because of the mis-feeding which often results from misalignment of the upper surfaces of the two stacks.
In presses and duplicating machines of the type here under discussion, the paper stock, after being printed, must be removed from the press or duplicator in a safe manner which allows the operator to handle the product as it is discharged from the press without stopping the press and thus cutting production rates. To facilitate such discharge of product and handling by the operator, various types of conveyors and/or receivers have previously been used on presses and duplicators to receive the printed stock, and move it to a location spaced from the press or duplicator where it can be gathered up by the operator and placed in boxes. In many of these receiver-conveyor devices, conveyor belts are provided upon which the printed paper stock is deposited upon discharge from the press or duplicator, and the belts then move the printed stock to a location where it is automatically overlapped or semi-stacked, ready for the operator to gather it up and place it, in the same order and arrangement as it leaves the press, in suitable containers.
In most of the receiver-conveyor devices of the type described, such apparatus is self-contained, and has a drive motor forming a part of the device and positively driving the rollers which support the conveying belts. In such systems, the receiver-conveyor continues to run when the press is off, and is not synchronized with the press speed unless approximate adjustments are made to approach such synchronization. Because of the inclusion of the motor and the drive mechanism by which the motor is connected to the rollers employed to drive the belts, receiver-conveyors of the type described are generally relatively heavy, and the inclusion of the independent drive therein increases their cost.
Also, in many of the receiver-conveyors used in this way, inadequate guides for the discharged paper stock are provided with the result that some of the sheets discharged from the press waft off of the conveyor belts, or slip to the side and must be picked up by the operator, or straightened out. Further, on occasion, some of the receiver-conveyors employed will become jammed due to an excessive number of sheets being deposited thereon faster than the conveyor can move these to the point of discharge, and such jams require the stopping of the press with a resultant loss in production. Further, the interface which is provided between many of the existing types of receiver-conveyor devices and the mechanism of the press results in jamming at the point of this interface, and operators occasionally attempt to reach into the mechanism to this location for the purpose of removing paper from the location of the jam. This presents a serious safety hazard which is particularly severe on those models of presses and duplicators which employ moving chains and sprockets for the purpose of moving the printed paper stock to the point of the interface between the receiver-conveyor and the printing mechanism.
Another problem which is occasionally encountered with receiver-conveyors of the driven belt type previously used, is that the frictional drive between the belt and the driven roller or rollers around which the belt is passed allows slipping to occur under heavy loads, with a resultant loss of conveying capacity and disfunction of the adjusted synchronism of the receiver-conveyor movement with the speed of operation of the press or duplicator.
Finally, where increased feed rates of paper stock to the press or duplicator are made possible by improved feeding systems of the sort described in my copending patent application, or where such increased production occurs as a result of attempted use of the two-up feeding system, existing receiver-conveyors are frequently incapable of operating consistently and reliably at speeds which are adequate to receive the very rapidly discharging finished stock.